1. Fields of the Invention
This invention relates to plastic underdrainage tube of the type buried along the soil to remove excess ground water from the soil, more particularly to a plastic underdrainage tube of generally reticular configuration in which longitudinal strands are closely spaced apart to define the drainage openings therebetween.
2. Description of the Prior Art
Underdrainage tubes, being subject to a high pressure or force by the surrounding soil, will require a high mechanical strength of withstanding such pressures. For this reason, conventional plastic underdrainage tubes, as illustrated in FIG. 1, have been thick-wall ones with a large number of minute pores 9 through the wall 8 thereof. However, such thick-wall type plastic tubes are almost disadvantageous from economic and resource-saving standpoints, in view of much material required to manufacture, Furthermore, due to the fact that excess numbers of the pores will weaken the tube strength against the surrounding pressures, the tube should be made to have a limited number of pores or opening ratio. Accordingly, the plastic tubes of higher drainage capacity have been difficult to be obtained.